Hi,
It seems to me that the following code is off-by-one bug.
http://lxr.linux.no/source/net/unix/af_unix.c#L191
http://lxr.linux.no/source/net/unix/af_unix.c?v=2.4.28#L182
I think
((char *)sunaddr)[len]=0;
should be
((char *)sunaddr)[len-1]=0;
Thanks.
Hi,
On Mon, Mar 28, 2005 at 05:00:05PM +0900, Tetsuo Handa wrote:
> Hi,
>
> It seems to me that the following code is off-by-one bug.
>
> http://lxr.linux.no/source/net/unix/af_unix.c#L191
> http://lxr.linux.no/source/net/unix/af_unix.c?v=2.4.28#L182
>
> I think
> ((char *)sunaddr)[len]=0;
> should be
> ((char *)sunaddr)[len-1]=0;
it seems you're right, or the first test in the function is wrong, so
there's clearly something to be fixed there :
static int unix_mkname(struct sockaddr_un * sunaddr, int len, unsigned *hashp)
{
if (len <= sizeof(short) || len > sizeof(*sunaddr))
^^^^^^^^^^^^^^^^^^^^^^
return -EINVAL;
if (!sunaddr || sunaddr->sun_family != AF_UNIX)
return -EINVAL;
if (sunaddr->sun_path[0]) {
((char *)sunaddr)[len]=0;
^^^^^^^^^^^^^^
len = strlen(sunaddr->sun_path)+1+sizeof(short);
return len;
}
*hashp = unix_hash_fold(csum_partial((char*)sunaddr, len, 0));
return len;
}
Then, I would propose this patch (both for 2.4 and 2.6) :
--- ./net/unix/af_unix.c.bad Sat Mar 26 07:42:49 2005
+++ ./net/unix/af_unix.c Mon Mar 28 10:11:25 2005
@@ -179,7 +179,7 @@
if (!sunaddr || sunaddr->sun_family != AF_UNIX)
return -EINVAL;
if (sunaddr->sun_path[0]) {
- ((char *)sunaddr)[len]=0;
+ ((char *)sunaddr)[len-1]=0;
len = strlen(sunaddr->sun_path)+1+sizeof(short);
return len;
}
Regards,
Willy
In article <[email protected]> (at Mon, 28 Mar 2005 17:00:05 +0900), Tetsuo Handa <[email protected]> says:
> It seems to me that the following code is off-by-one bug.
>
> http://lxr.linux.no/source/net/unix/af_unix.c#L191
> http://lxr.linux.no/source/net/unix/af_unix.c?v=2.4.28#L182
>
> I think
> ((char *)sunaddr)[len]=0;
> should be
> ((char *)sunaddr)[len-1]=0;
Well, 2.2 has some comment on this:
static int unix_mkname(struct sockaddr_un * sunaddr, int len, unsigned *hashp)
{
if (len <= sizeof(short) || len > sizeof(*sunaddr))
return -EINVAL;
:
if (sunaddr->sun_path[0])
{
/*
* This may look like an off by one error but it is
* a bit more subtle. 108 is the longest valid AF_UNIX
* path for a binding. sun_path[108] doesnt as such
* exist. However in kernel space we are guaranteed that
* it is a valid memory location in our kernel
* address buffer.
*/
if (len > sizeof(*sunaddr))
len = sizeof(*sunaddr);
((char *)sunaddr)[len]=0;
len = strlen(sunaddr->sun_path)+1+sizeof(short);
return len;
}
:
--
Hideaki YOSHIFUJI @ USAGI Project <[email protected]>
GPG FP: 9022 65EB 1ECF 3AD1 0BDF 80D8 4807 F894 E062 0EEA
In article <[email protected]> (at Mon, 28 Mar 2005 17:21:08 +0900 (JST)), YOSHIFUJI Hideaki / 吉藤英明 <[email protected]> says:
> > It seems to me that the following code is off-by-one bug.
:
> Well, 2.2 has some comment on this:
So, I'd suggest to put the comment back to 2.4/2.6 instead.
(Note: net/socket.c refers this around MAX_SOCK_ADDR definition.)
Signed-off-by: Hideaki YOSHIFUJI <[email protected]>
===== net/unix/af_unix.c 1.73 vs edited =====
--- 1.73/net/unix/af_unix.c 2005-03-10 13:42:53 +09:00
+++ edited/net/unix/af_unix.c 2005-03-28 17:31:33 +09:00
@@ -188,6 +188,15 @@
if (!sunaddr || sunaddr->sun_family != AF_UNIX)
return -EINVAL;
if (sunaddr->sun_path[0]) {
+ /*
+ * This may look like an off by one error but it is
+ * a bit more subtle. 108 is the longest valid AF_UNIX
+ * path for a binding. sun_path[108] doesnt as such
+ * exist. However in kernel space we are guaranteed that
+ * it is a valid memory location in our kernel
+ * address buffer.
+ */
+ if (len > sizeof(*sunaddr))
((char *)sunaddr)[len]=0;
len = strlen(sunaddr->sun_path)+1+sizeof(short);
return len;
--
Hideaki YOSHIFUJI @ USAGI Project <[email protected]>
GPG FP: 9022 65EB 1ECF 3AD1 0BDF 80D8 4807 F894 E062 0EEA
In article <[email protected]> (at Mon, 28 Mar 2005 17:39:38 +0900 (JST)), YOSHIFUJI Hideaki / 吉藤英明 <[email protected]> says:
> So, I'd suggest to put the comment back to 2.4/2.6 instead.
> (Note: net/socket.c refers this around MAX_SOCK_ADDR definition.)
>
> Signed-off-by: Hideaki YOSHIFUJI <[email protected]>
Oops, sorry, I made a mistake when I did copy-n-paste...
Signed-off-by: Hideaki YOSHIFUJI <[email protected]>
===== net/unix/af_unix.c 1.73 vs edited =====
--- 1.73/net/unix/af_unix.c 2005-03-10 13:42:53 +09:00
+++ edited/net/unix/af_unix.c 2005-03-28 17:45:26 +09:00
@@ -188,6 +188,14 @@
if (!sunaddr || sunaddr->sun_family != AF_UNIX)
return -EINVAL;
if (sunaddr->sun_path[0]) {
+ /*
+ * This may look like an off by one error but it is
+ * a bit more subtle. 108 is the longest valid AF_UNIX
+ * path for a binding. sun_path[108] doesnt as such
+ * exist. However in kernel space we are guaranteed that
+ * it is a valid memory location in our kernel
+ * address buffer.
+ */
((char *)sunaddr)[len]=0;
len = strlen(sunaddr->sun_path)+1+sizeof(short);
return len;
--
Hideaki YOSHIFUJI @ USAGI Project <[email protected]>
GPG FP: 9022 65EB 1ECF 3AD1 0BDF 80D8 4807 F894 E062 0EEA
On Mon, Mar 28, 2005 at 05:39:38PM +0900, YOSHIFUJI Hideaki / ?$B5HF#1QL@ wrote:
> + /*
> + * This may look like an off by one error but it is
> + * a bit more subtle. 108 is the longest valid AF_UNIX
> + * path for a binding. sun_path[108] doesnt as such
> + * exist. However in kernel space we are guaranteed that
> + * it is a valid memory location in our kernel
> + * address buffer.
icky pointless white space?
> + */
> + if (len > sizeof(*sunaddr))
what?
Hi,
I understood it will not cause trouble.
Thanks a lot.
In article <[email protected]> (at Mon, 28 Mar 2005 11:25:39 +0200 (MEST)), Jan Engelhardt <[email protected]> says:
>
> On Mar 28 2005 17:39, YOSHIFUJI Hideaki / 吉藤英明 wrote:
>
> >+ * This may look like an off by one error but it is
> >+ * a bit more subtle. 108 is the longest valid AF_UNIX
> >+ * path for a binding. sun_path[108] doesnt as such
> >+ * exist. However in kernel space we are guaranteed that
> >+ * it is a valid memory location in our kernel
> >+ * address buffer.
> >+ */
>
> Now, does 2.6. _still_ guarantee that 108 is a valid offset?
Yes, it does.
--yoshfuji